The present disclosure relates to electronic circuits, systems and apparatuses, and in particular, to systems and methods for charging a battery.
Many modern electronic systems rely on one or more batteries for power. The batteries are typically recharged by connecting the system to a power source (e.g., an alternating current (AC) power outlet) via an AC-DC power adapter and cable, for example. FIG. 1 illustrates battery charging in a typical electronic device. In this example, a power adapter 102, such as an AC-DC converter, is connected to a power source 101. Power adapter 102 may provide a direct current (DC) voltage and current to electronic device 103 via a cable 120. Voltage and current from power adapter 102 are received by a power interface, such as a power management integrated circuit (PMIC), which may convert the voltage and current from adapter 101 to different voltages and currents to drive various system components, such as one or more processors 111, communications electronics (e.g., radio frequency (RF) transceivers) 112, and one or more input/output devices 113, such as a touch screen display our audio system, for example. When disconnected from an external power source, power interface 110 may receive voltage and current from battery 114 to power the internal components, for example.
Power interface 110 may include a battery charging circuit 115 for charging battery 114 when the battery is discharged. One problem associated with battery chargers is power dissipation. Cable 120 may include resistance leading to thermal power dissipation as well as a reduction of the input voltage from the power adapter. Accordingly, the voltage at the input of the battery charger may be less than the voltage at the output of the power adapter due to current in the cable 120. To reduce this voltage drop, some systems may use higher adapter voltages, which will effectively reduce the amount of current required to achieve the same power level. However, higher adapter voltages can cause larger power dissipation in battery charger circuitry. For example, higher voltages across switching transistors in the battery charger may cause increases in power dissipation during charging due to increased switching losses every turn-on/off cycle. Additionally, higher input voltages can cause increased current ripple in a battery charger's inductor(s), which can result in higher conduction losses and core losses, for example. Therefore, being able to optimize power dissipation during the battery charging process is an ongoing challenge for battery operated systems.